PE - Reactions and methods Flashcards
Elek test
- A strip of filter paper impregnated with diphtheria antitoxin is buried just beneath the surface of the agar
- Strains to be tested are streaked with known positive and known negative toxigenic strains on the agar’s surface in a line across the plate, and at a right angle to the antitoxin paper strip.
- After incubation for 24 hours at 37 degrees Celsius, plates are examined with transmitted light for the presence of fine precipitin lines at a 45-degree angle to the streaks.
- The presence of precipitin lines indicates that the strain produced toxin that reacted with the antitoxin.
Aspecific serological tests for the diagnosis of syphilis: Wasserman reaction
Complement fixation test for syphilis:
- serum is diluted (Ab)
- add cardiolipin
- add complement
- add Anti sheep-blood Ab
- no-lysis = positive / yes-lysis = negative
Aspecific serological tests for the diagnosis of syphilis: RPR
RPR–test (Rapid Plasma Reagin)
- Antigen = cardiolipin suspension attached to latex particles
- A drop of the cardiolipin latex suspension is placed onto the surface of a glass slide, then mixed with a drop of the serum.
- Negative: Cardiolipin latex suspension remains intact
- Positive: Cardiolipin latex is agglutinated and sediments as rough granula
Aspecific serological tests for the diagnosis of syphilis: VDRL
VDRL–test (Venereal Disease Research Laboratory)
- cardiolipin suspension placed on a glass slide
- mixed with a drop of the inactivated serum
- Negative: Cardiolipin suspension remain dispersed
- Positive: Cardiolipin forms visible clumps when combining with reagent
Influenzavirus hemagglutination (HA)
- virus with hemagglutinin on it’s surface => clumping RBCs
- bind to sialic receptor on the surface of RBC
- lattice formation => positive
- precipitation => not enough virus to form lattice
(e.g. Influenzavirus; measles; mumps)
Haemagglutination inhibition (HAI)
- virus with hemagglutinin on it’s surface => clumping RBCs
- bind to sialic receptor on the surface of RBC
- checking for Abs for the virus
- lattice formation => negative for Ab
- precipitation => enough Ab are present
complement fixation (CF)
- serum is diluted (Ab)
- add Ag of intrest
- add complement
- add Anti sheep-blood Ab
- no-lysis = positive / yes-lysis = negative
Diagnosis of fresh rubella infection (HAI)
- virus with hemagglutinin on it’s surface => clumping RBCs
- bind to sialic receptor on the surface of RBC
- checking for Abs for the virus
- lattice formation => negative for Ab
- precipitation => enough Ab are present
- IgG => immunization / past infection
- IgM (IgG) => Acute infection
ELISA
for: HIV-1 ,2, hepatitis A, B, C
Comp. ELISA - The amount of color is inversely proportional to the amount of Ab in serum. (Hep - A, B)
indirect ELISA - Wel coated by Ag, Patient serum + anti human Ab. (Hep - C)
Verification of HIV-1 infection by Western blot
- An antibody is then added to the solution which is able to bind to
its specific protein - The antibody ahs an enzyme or dye attached to it which cannot be seen at this time
- The location of the antibody is revealed by incubation, when a colorless substrate attach to the enzyme and change color
Phage typing
- using a specific bacteriophage to determine a bacterial strain that outbreaks
Blood cultures. Rules and regulations of collecting
sample(s) for blood culture bottles.
- 6 bottles, collect at different times.
- collect both aerobic and anaerobic Blood cultures bottles.
- disinfect the area of venipuncture + don’t use cannula
Gram staining (steps and mode of action)
- Crystal violet 2min -> Iodine 1min -> 96% Alc. -> Fuchsin or safranin -> Dry filter paper
- G + purple (Alc does not wash CV from PG); G – Red
Ziehl-neelsen stain
- Carbolfuchsin -> heat -> Red -> Alc + Mycolic acids stays red -> Methylene blue -> non-mycolic -> Blue
- Mycobacterium TB, laprae; nocardia
